JP2001295025A - Two-stage ain-pvd improving film characteristic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for depositing aluminum nitride layers on a substrate in a treatment chamber. SOLUTION: A first aluminum nitride layer is vapor deposited on a substrate at a first chamber pressure, and then a second aluminum nitride layer is vapor deposited on the resultant aluminum nitride nucleation layer at a higher second chamber pressure. The first aluminum nitride layer is vapor deposited by sputtering an aluminum target at about 1.5-3 millitorr chamber pressure in a nitrogen and inert gas plasma in the treatment chamber. The second aluminum nitride layer is vapor deposited by carrying out sputtering at about 5-10 millitorr chamber pressure. The above treatments can be performed in the same treatment chamber while maintaining the temperature of the substrate at preferably 125-500 deg.C. By this method aluminum nitride having preferred crystal orientation can be obtained at high deposition rate, and the characteristics of the layers can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to metallization processes for fabricating semiconductor devices, and more particularly to a method for depositing aluminum nitride films.

[0002]

2. Description of the Related Art A surface acoustic wave device (SAW) and a bulk acoustic wave device (BAW) device are circuit devices that convert electric signals into acoustic waves and convert acoustic waves into electric signals to perform signal processing. Due to the ability to transfer acoustic waves to electrical data and electrical data to acoustic waves, SAW and BAW devices have been widely used in filters, resonators, delays, and other electroacoustic devices in communications and other related fields. In particular, S
AW and BAW are very promising in the mobile communication field because their acoustic wave devices have a simple structure with wireless filter characteristics effective for use in mobile communication electronics. Recently, demand for faster information transmission in the mobile radio communication field has been increasing, and demand for SAW and BAW operating at a high frequency has been increasing.

[0003] As one example, a SAW device forms an electrode of a conductive film such as a metal, for example, an interdigital converter (IDT) on a piezoelectric substrate, and the electrode mutually converts an electric signal and a surface acoustic wave. It is manufactured as follows. The characteristics of the surface acoustic wave are determined by the propagation characteristics of the electrodes on the piezoelectric substrate. In order for the acoustic wave device to operate at a higher frequency, the propagation speed of the acoustic wave between the piezoelectric substrate and the electrode must be high.

[0004] Piezoelectric materials having desirable electromechanical properties, such as high propagation speed, high frequency response, high coupling coefficient, etc., are known as bulk wave propagation media, surface wave propagation substrates, and thin materials used as mechanical resonators. It is obtained by combining piezoelectric films. Thus, one preferred means of obtaining a high frequency operating acoustic wave device is to deposit a high speed acoustic wave propagation film on a piezoelectric film or substrate.

[0005] Aluminum nitride (AlN) films have been considered as attractive piezoelectric materials for making on-chip high frequency gigahertz band acoustic devices (above 2 GHz). Because about 6000m of aluminum nitride
Per second, which has a high propagation velocity of about 0.07, which indicates the efficiency of converting electric energy to acoustic wave energy, good piezoelectric properties, and attractive electromechanical properties such as high heat resistance. is there. Such electromechanical properties depend on physical parameters of the film, including crystal structure, crystal orientation, film thickness, and the like. By optimizing the parameters of the film, the desired electromechanical properties can be created for use specifically with SAW devices. Therefore, aluminum nitride with high crystal quality, favorable grain orientation (often referring to crystal orientation) and uniform thickness, for use in SAW applications, especially for the production of on-chip acoustic wave devices for integrated circuits Many efforts have been made in the manufacture of

[0006] Typically, thin aluminum nitride (AlN) films are deposited by chemical vapor deposition (CVD) and molecular beam epitaxy (MBE) techniques. Although these AlN films have shown very promising acoustic wave properties when evaluated by the surface acoustic wave technique, these deposition methods of AlN films usually require substrates to be at temperatures above 1000 ° C. This high deposition temperature is not suitable for semiconductor integrated circuit manufacturing methods for manufacturing modern on-chip acoustic wave devices.

[0007] One alternative method of depositing AlN at a low temperature not exceeding 500 ° C. is to deposit an AlN film by PVD sputtering. However,
Aluminum nitride layers deposited by the PVD method tend to have a random crystalline orientation in the resulting layer. The aluminum nitride crystal structure randomly generated on the substrate becomes a polycrystalline film having no preferable grain orientation. Because the random crystal orientation produces a film with low coupling coefficient, low sound propagation speed and high propagation loss,
This causes poor conversion between the electronic signal and the surface acoustic wave.
Thus, the orientation of crystals in a polycrystalline film is a key material parameter that affects the SAW and BAW properties of the deposited film, and the formation of crystalline orientation in an AlN film is a film with excellent acoustic properties. Is important for the formation of

[0008] Thin film deposition processes typically begin with the deposition of an isolated nucleation site. In PVD deposition, these sites are created when the individual sputtered sites of the target strike the substrate, and then another such site is deposited on the substrate. In CVD deposition, nucleation sites occur where predecessor nuclei deposit on the substrate. In practice, the difference in the growth rates of the nucleation sites determines the orientation of the film. In particular, films deposited by PVD sputtering are believed to produce polycrystalline films that grow from random nucleation sites and grow. Nucleation sites that grow in a direction perpendicular to the substrate surface with a crystal orientation exhibiting a fast growth rate will appear because they predominate over sites having an orientation exhibiting a slow growth rate. The film structure resulting from the PVD sputtering process has many grains of different sizes and many crystal orientations.

One method for producing an aluminum nitride film having a preferred degree of crystal orientation by PVD is disclosed in Ishihara et al.
Control of Preferred Orientation of N Film ", Thin Solid
Films 316 (1998), pages 152-157. Ishihara et al. Provide a sputtering system for aluminum nitride deposition having a preferred crystallographic orientation. However, the processing method of Ishihara et al. Produces a film with large stress and uneven thickness. High film stress results in defects in the film layer that adversely affect the electromechanical properties of the aluminum nitride film. In addition, since the transmission frequency and frequency response of the SAW device are highly dependent on the uniformity of the film thickness, non-uniform films will have inconsistent and inconsistent SAW performance. Furthermore, while practically satisfactory deposition rates are above about 1000 angstroms / minute, Ishihara et al.'S processing methods struggle with deposition rates lower than 200 angstroms, which limits the practicality of that processing method. is there.

[0010]

Accordingly, there is a need for a method of depositing an aluminum nitride film having a favorable crystal orientation and improved film properties at a high deposition rate.

[0011]

SUMMARY OF THE INVENTION The present invention generally provides a two-step process for forming an aluminum nitride layer on a substrate using physical vapor deposition. In one aspect of the invention, the method of depositing comprises depositing the first aluminum nitride layer with a first aluminum nitride layer, preferably between about 1.5 mTorr and about 3.0 mTorr.
Depositing at a chamber pressure to provide a nucleation layer having a preferred degree of crystal orientation, and forming the second aluminum nitride layer at a first chamber pressure greater than the first chamber pressure, preferably between about 5 mTorr and about 10 mTorr. Depositing at a chamber pressure of 2. The first aluminum nitride layer is suitably deposited by sputtering an aluminum target in a nitrogen plasma containing a trace amount of inert gas, and the second aluminum nitride layer is formed by sputtering the aluminum target in a plasma of nitrogen and an inert gas. To be deposited. The first and second deposition steps are performed at about 125 ° C. and about 500 ° C. in the same PVD chamber.
It is preferably carried out at a substrate temperature of between.

In another aspect of the invention, a first nitriding gas is introduced into a processing chamber to generate a first chamber pressure, and an aluminum target is sputtered to deposit a first aluminum nitride layer. Stage and second
Introducing a nitriding gas into the processing chamber to generate a second chamber pressure higher than the first chamber pressure, and sputtering the aluminum target to form a second chamber pressure.
Depositing an aluminum nitride layer on the substrate, an aluminum nitride film is deposited on the substrate in the processing chamber. This deposition process results in a preferred crystal orientation with improved film properties. This deposition process also provides a high deposition rate for forming aluminum nitride films.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the manner in which the features, advantages and objects of the invention set forth above are achieved, the above is briefly summarized above by reference to embodiments of the invention as illustrated in the accompanying drawings. The present invention will be described in more detail. The accompanying drawings show only representative embodiments of the invention and do not limit the scope of the invention, as the invention is capable of accepting other equally effective embodiments. It should be noted.

[0014]

DETAILED DESCRIPTION OF THE INVENTION The present invention generally provides a two-step process for depositing a piezoelectric film on a substrate. More specifically, the present invention provides that the first aluminum nitride layer is deposited at a first chamber pressure and the second aluminum nitride layer is deposited at a second chamber pressure higher than the first chamber pressure. It is an object of the present invention to provide a two-step process for forming an aluminum nitride layer having improved film properties. The two-stage deposition method uses an aluminum target,
Sputtering in a plasma of a nitriding gas (preferably nitrogen) and an inert gas (preferably argon) at a chamber pressure of between about 1.5 mTorr and about 3 mTorr; Sputtering in a plasma of a gas (preferably nitrogen) and an inert gas (preferably argon) at a chamber pressure between about 5 mTorr and about 10 mTorr. The two-step process of depositing the film is preferably performed at a substrate temperature between about 125 ° C and 500 ° C.
The present invention has the advantage that at a high deposition rate, an aluminum nitride layer having a preferred degree of grain orientation can be produced with reduced film stress and improved thickness uniformity.

[0015] The method of the present invention can be implemented using a PVD chamber commercially available from Applied Materials, Santa Clara, California. PVD
The general features of the chamber are described below. It should be understood that other than the PVD chambers known to the inventor and described below, other chambers are available and can be modified to utilize the advantages of the method according to the present invention.

The PVD chamber 36 generally includes a chamber enclosure 102, a target 104, a substrate support 106, a gas inlet 108 and a gas outlet 110. Chamber circumference 1
02 has a chamber bottom 112 and a chamber side wall 114. A slit valve 115 is attached to the chamber side wall 114 so that the substrate 116 can be easily inserted into and removed from the PVD chamber 36. The substrate support 106 is located at the bottom 11 of the chamber.
2 through a substrate support lift assembly 118. Typically, a temperature control element (not shown), such as a heater, is mounted within the substrate
6 is controlled. The substrate support 106 is made of stainless steel and the temperature control element preferably comprises a platinum / rhodium heater coil. Substrate support lift assembly 118
Moves the substrate support 106 vertically between the substrate transfer position and the substrate processing position. The lift pin assembly 120 is mounted on the substrate 11
6 is lifted away from the substrate support 106, and the substrate 116 is lifted.
To facilitate transfer between the chamber and a robot blade (not shown) for moving substrates into and out of the chamber.

A target 104 is located on top of the chamber enclosure 102. Preferably, the target 104 is located directly above the substrate support 106. Target 104
Has a backing plate 122 that typically supports a plate of sputtering material 124. A typical target material for an aluminum nitride film is aluminum used in the reactive sputtering process referred to herein. The receiving plate 122 is a flange portion 12 fixed to the chamber surrounding 102.
6. Seal 128, preferably an O-ring
Is the flange portion 126 of the receiving plate 122 and the chamber surrounding 1
02 to maintain a vacuum in the chamber during processing. The magnet assembly 130 is mounted on the receiving plate 12
2 to enhance the sputtering of the target material by applying a magnetic field that increases (by confining electrons) the plasma density at the sputtering surface of the target.

A lower shield 132 is located within the chamber,
The inner surface of the chamber enclosure 102 is shielded from being deposited.
The lower shield 132 extends from the upper portion of the chamber side wall 114 to the peripheral edge of the processing position of the substrate support 106. Clamping ring 134 is used and inner end 13 of lower shield 132
6 so as to be movable. When the substrate support 106 moves into the processing position, the inner end 136
06, the peripheral portion 138 of the substrate 116 engages the inner end 133 of the clamp ring 134 and lifts the clamp ring 134 from the inner end 136 of the lower shield 132.
The clamp ring 134 serves to clamp or hold the substrate 116 while shielding the peripheral portion 138 of the substrate 116 during the deposition process. Alternatively, a shield cover ring (not shown) is placed over the inner end of the lower shield instead of the clamp ring 134. As the substrate support moves to the processing position, the inner edge of the shielding cover immediately comes to a position on the peripheral portion of the substrate, shielding the peripheral portion of the substrate support 106 from being deposited.

Preferably, the upper shield 140 is the lower shield 1
32 and extends from the top of the chamber sidewall 114 to the peripheral edge 142 of the clamp ring 134.
Preferably, the material of the upper shield 140 is made of the same material as the material of the target, that is, a metal such as aluminum or titanium. The top shield 140 is preferably a floating ground top shield, where plasma ionization is high compared to the ground top shield. If the plasma ionization is large, the supply of ions affecting the target 104 increases, and the target 1
The deposition rate increases because the deposition rate increases from 04.
Alternatively, the top shield 140 can be grounded during the deposition process.

The chamber side wall 114 of the chamber enclosure 102
A gas outlet 108 attached to the upper shield 140 and the lower shield 1 directs process gas into the chamber enclosure 102.
32 into the sink processing cavity 146. The processing cavity 146 is bounded by the target 104, the substrate 116 disposed on the substrate support 106 in the processing position, and the top shield 140. Typically, argon is introduced through the gas inlet 108 as a processing gas for the plasma. A gas outlet 110 is located on the chamber sidewall 114 to evacuate the chamber prior to the deposition process and simultaneously control the chamber pressure during the deposition process. Preferably, gas outlet 110 is connected to exhaust valve 156 and exhaust pump 158.
Having. The exhaust valve 156 controls the degree of communication between the inside of the chamber 36 and the exhaust pump 158.

A power supply 152 is electrically connected to the target 104 to bias the target 104. The power source 152 can include a DC generator connected to the target and a DC matching network. A power supply 152 supplies energy to the processing cavity and directs and maintains a plasma of the processing gas in the processing cavity during the deposition process.

A gas outlet 110 is located on the chamber sidewall 114 to evacuate the chamber prior to the deposition process and to control the chamber pressure during the deposition process. Preferably, the gas outlet has an exhaust valve 156 and an exhaust pump 158. The exhaust valve 156 controls the degree of communication between the inside of the chamber 36 and the exhaust pump 158. Exhaust pump 1
58 preferably includes a cryogenic pump with a turbomolecular pump to minimize the time to pump down the chamber.
Alternatively, exhaust pump 158 comprises a low and high pressure pump, or a combination of low and high pressure pumps.

Referring to FIG. 1, the sputtering process is performed in a processing area, or processing cavity 146, located between the sputtering target 104 and the substrate 116, preferably made of aluminum. The target 104 is electrically insulated from the chamber 36 and acts as a processing electrode for generating a sputtering plasma. During the sputtering process, a sputtering gas, typically a noble gas such as argon or xenon, is introduced into the processing cavity 146 of the chamber 36. Power is then applied so that the target is a negative electrode, and an electric field is formed in the chamber 36 such that the chamber walls and, if necessary, the substrate 116 disposed in the chamber 36 are electrically grounded. You. Chamber 3
The combined electric field in 6 ionizes the sputtering gas to generate a sputtering plasma that sputters the target 104 to deposit material on the substrate. In a sputtering process, the plasma typically has a power level to the sputtering target of about 100 to about 20,0.
00 watts, more usually from about 100 to about 10,000
0 watts, more preferably from about 4,000 to about 7000
Generated by applying a DC or RF (high frequency) voltage of 0 watts.

Control System Referring to FIG. 2, the process of the present invention can be performed using a computer program product 161 which, for example, is connected to a memory system with peripheral control elements, for example. It runs on a common computer system having a central processing unit (CPU), such as the 68400 processor available from Synergy Microsystems of California. The computer program code can be written in any common computer readable programming language, for example, 68000 assembly language, C, C ⁺⁺ , Java, or Pascal. The appropriate program code is entered into a file or files using a conventional text editor and stored or embodied in a computer usable medium, such as a computer memory system. If the input code text is in a high-level language, the code is compiled and the resulting compiled code is then linked with the object code of the precompiled Windows library routines. To execute the linked and compiled object code,
A system user invokes the object code, causing the computer system to load the code into memory, which causes the CPU to read and execute the code and perform the tasks specified in the program.

FIG. 2 shows an exemplary block diagram of the hierarchical control structure of the computer program 161. The user inputs the processing set number and the processing chamber number using the light pen interface according to the menu or the screen displayed on the CRT monitor. The tile processing set
This is a predetermined set of processing parameters required to execute a specific process, and is recognized by a predetermined set number. The process selection subroutine 162 may include (i) a recognized process chamber, or a desired process chamber if a multi-chamber system is used, and (i)
i) Identify the desired set of processing parameters required to operate the processing chamber to perform the desired processing. Processing parameters for executing a specific process are as follows:
For example, processing gas composition and flow rate, temperature, chamber pressure, D
It relates to plasma conditions, such as C power level, and processing conditions, such as chamber dome temperature, and is provided to the user in the form of processing conditions. The parameters specified by the processing conditions are input using a light pen / CRT monitor (not shown).

The processing sequencer subroutine 163 accepts a particular processing chamber and set of processing parameters from the processing selection subroutine 162 and includes program code for controlling the operation of the various processing chambers. The sequencer subroutine 163 arranges the selected processes in a desired order because multiple users can enter the process set number and process chamber number, or a single user can enter multiple process set numbers and process chamber numbers. Schedule and work. Preferably, the sequencer subroutine 163 (1) monitors the operation of the processing chamber to determine whether the chamber is being used;
(2) determining what processing is being performed in the chamber being used, and (3) performing the desired processing based on the availability of the processing chamber and the type of processing to be performed. The execution program of the stage is provided. Common methods of monitoring the processing chamber, such as polling, can be used. When scheduling which process to execute, the sequencer subroutine 163 takes into account the current state of the chamber being used and considers the desired process conditions for the selected process or the "Request It can be designed to be compared to "when" or another relevant factor that the system programmer requires to include in order to prioritize scheduling.

After the sequencer subroutine 163 has determined which process chamber and process set combination is to be executed next, the sequencer subroutine 163 stores the specific process set parameters in the chamber management subroutine 164.
The process set is executed by passing to A-C, the chamber management subroutine
Alternatively, a plurality of processing tasks of another chamber (not shown) are controlled according to a set of tile processing determined by the sequencer subroutine 163.

Once the sequencer subroutine 163 determines which processing chamber and processing set combination to execute next, the sequencer subroutine 163 stores the specific processing set parameters into the chamber management subroutine 164.
The chamber management subroutine controls a plurality of processing tasks in separate processing chambers based on the processing set determined by the sequencer subroutine 163 by passing them to AC. For example, the chamber management subroutine 164A performs the processing chamber 36 described in FIG.
Has a program code for controlling the PVD processing operation in the inside.

The chamber management subroutine 164 also controls various chamber element subroutines or program code modules that control the chamber elements required to execute the selected process set. Examples of the chamber element subroutine include a substrate positioning subroutine 165, a processing gas control subroutine 166, and a pressure control subroutine 16.
7, a heater control subroutine 168 and a plasma control subroutine 169. One skilled in the art will appreciate that the chamber 36 (FIG. 1)
It will be appreciated that different chamber control subroutines may be included, depending on what processing is required to be performed in FIG. In operation, the chamber management subroutine 164A selectively schedules or calls processing element subroutines associated with the particular process to be performed. Chamber management subroutine 164A
Is performed in the same manner as using the sequencer subroutine 163 that executes the processing set with the processing chamber. Generally, the chamber management subroutine 164A includes steps for monitoring various chamber elements, determining which elements are required to operate based on process parameters for the process to be performed, and monitoring and determining. Executing a chamber element subroutine in response to the step.

Deposition Process A preferred process sequence performed using the above-described system of the present invention will now be described. Preferably, in the piezoelectric film, a hexagonal crystal orientation (0002) of the aluminum nitride, often referred to as a (001) cubic crystal orientation, is produced. This is because the orientation increases the electromechanical coupling coefficient and is superior in electromechanical properties to the orientation of other aluminum nitride crystals. However, aluminum nitride is difficult to grow in the (0002) crystallographic orientation in the normal PVD process. The present invention provides a novel two-step deposition process, wherein the deposition rate is about 100.
An aluminum nitride film having a practically preferred (0002) crystal orientation of 0 Å / min or more is obtained. The first aluminum nitride deposition step of the present invention controls the degree of crystal orientation by promoting the growth of nucleation sites formed with a preferred (0002) crystal orientation. The second aluminum nitride deposition step of the present invention decouples the deposition rate of aluminum nitride from the choice of crystal orientation.

[0031] For the aluminum nitride deposition process, preferably the same physical vapor deposition (PVD) chamber is used for both stages of the process, where the substrate is preferably maintained at a temperature between about 125 ° C and about 500 ° C. Is done. The substrate is introduced into a PVD chamber containing an aluminum target as described above.

In the first aluminum nitride deposition step, a process gas, including a nitriding gas such as nitrogen and an inert gas such as argon, is introduced into the PVD chamber for a period of time, and the pressure in the first chamber is reduced to about Between 1.5 mTorr and about 3 mTorr, an aluminum nitride film having a (0002) orientation is deposited. Once the processing gas has brought the chamber to the desired pressure, a power of about 4000 watts (4 kW) to about 7000 watts (7 kW) is applied to the target and a plasma is applied. The process gas plasma sputters the aluminum target and deposits it directly on the substrate with nitrogen, or produces aluminum species that react with the nitrogen species contained in the plasma to produce aluminum nitride, which is then deposited on the substrate surface .

In practice, it is considered that the rate of formation of nucleation sites having an orientation such as the preferred (0002) orientation and the corresponding growth rate of nucleation sites are controlled by the deposition rate of the crystal growth unit. In particular, the orientation and the growth of the nucleation site depend on the number of bonds present under the growth unit. If the growing unit is an atom such as Al or N, the preferred crystallographic orientation (0002) will develop and dominate the other formed crystallographic orientations. The growth unit is Al-
In the case of a dimer such as N, a crystal orientation other than the (0002) orientation is formed. The formation of atomic and dimeric growth units is affected by the interaction of Al and N species during the deposition process. The more interactions between the Al and N species, the more likely dimeric growth units will be formed. Thus, by controlling the interaction between the Al and N species, a favorable degree of crystal orientation can be achieved.

Controlling the pressure between about 1.5 mTorr and about 3 mTorr is the preferred method to minimize the interaction of Al and N species during sputtering,
This improves the formation and growth of nucleation sites having a high (0002) orientation. The deposited (0002) oriented film provides the preferred crystalline orientation for the subsequently deposited aluminum nitride layer. However, when aluminum nitride is deposited at low chamber pressures, the deposition rate is reduced, resulting in highly oriented films exhibiting high compressive stress and increased thickness non-uniformity. To minimize such undesirable film properties, the first aluminum nitride layer is preferably constructed to a thickness not exceeding about 300 angstroms. However, depending on the application, the first aluminum nitride film may be deposited thick.

In the second aluminum nitride deposition step, the chamber pressure is increased to between about 5 mTorr and about 10 mTorr. The processing gas of the second deposition stage is also preferably a nitriding gas such as nitrogen and argon (A
r). Preferably, increasing the pressure in the second deposition stage is achieved by increasing the flow rates of the inert gas and the nitrogen-containing gas. Once the desired chamber pressure and process gas flow rates are achieved, a plasma is generated by applying between about 4 kW and about 7 kW of power to the target. The process gas plasma sputters the aluminum target, which produces aluminum species, which react with the nitrogen species to form aluminum nitride, which is then deposited on the substrate. (Al can also be formed on another surface of the target and chamber and on the substrate.) The second deposition step is performed at a high chamber pressure, the deposition rate is high, and the film has a low tensile force rather than a high compressive stress. And the uniformity of the film thickness is improved.

By producing a film that does not have the preferred (0002) crystallographic orientation, a high deposition rate is obtained in the second deposition step. In practice, increasing the interaction between Al and N species by using a "long throw" PVD chamber to increase the time for the interaction to take place and / or to increase the reaction capacity of the species. Can be
The AlN dimer will grow. Preferably, the chamber pressure is between about 5 mTorr and about 10 mTorr, increasing the ability of the nitrogen and aluminum species to react and form AlN dimers. If the deposition is controlled at a high pressure, a large amount of plasma and sputtering material can be obtained,
The result is that the deposition rate is higher and the crystal growth is faster than that obtained by using only Al and N species alone. In addition, the crystal structure formed from the dimer growth unit is probably (00
02) smaller than the crystal structure formed by the atomic growth unit of crystal orientation, separated during the sputtering process, and
02) The deposition rate is higher than the crystal orientation deposition.

In a two-stage deposition process, the first aluminum nitride layer provides a preferred crystal orientation to the growing second aluminum nitride layer deposited during the second deposition stage. The two-step deposition process produces a film with a first layer exhibiting the desired crystal orientation and a second layer having a higher deposition rate and improved film properties. Therefore, the present invention controls the chamber pressure of the deposition and thus the composition of the reactive species, thereby controlling the degree of crystal orientation of the film and the achieved deposition rate.

In addition to the interaction of the plasma species to determine the crystal orientation, it is believed that in practice the improved film properties are affected by higher chamber pressure deposition mechanisms. The relatively high chamber pressure promotes higher collision and dimer formation rates, where the dimer converts the pre-impact kinetic energy of the Al and N species into binding energy. Formed, thereby producing Al-N species with low kinetic energy after impact. Because the active particle bombard during deposition exhibits compressive stress, the low kinetic energy of the dimer species being deposited on the substrate forms a film with low compressive stress. This low compressive stress film adheres more strongly to adjacent materials, such as the substrate, and has few layer problems such as film cracking and film discontinuity. Thus, the deposition process of the present invention solves the film stress problem by combining a thin layer of high stress material with a large amount of deposition of a material having low stress properties, thereby reducing the integrated aluminum nitride of low overall stress. Form a film.

Furthermore, as the collision rate of the dimer species increases and the kinetic energy decreases, the distribution in the plasma will be more uniform, and a stable plasma density will be obtained over the entire substrate, resulting in a more uniform distribution on the substrate. And yields films with improved thickness uniformity. Those skilled in the art will appreciate that while maintaining the basic characteristics of the process,
It will be appreciated that the two-step deposition process needs to be modified for the performance of the present invention in relation to chamber pressure, temperature, and various equipment.

Example of Two-Step Deposition An aluminum nitride layer was deposited according to the present invention as shown below. The substrate may be a processing platform (e.g., Applied Mater, Santa Clara, CA).
Eudra Platform available from ials
m (R)) and transferred to the PVD chamber. Nitrogen was added at a flow rate of about 56 sccm, and argon was added into the chamber at a flow rate of about 9 sccm for about 60 seconds until the chamber pressure stabilized at about 3.1 mTorr. A plasma was generated and aluminum was sputtered from the aluminum target in a nitrogen / argon plasma. The target was sputtered at a power of about 4 kW for about 15 seconds, producing an aluminum nitride layer having a thickness not exceeding about 300 Å.

Next, on the first aluminum nitride layer,
A second aluminum nitride layer was deposited. Nitrogen and argon are flowed into the chamber at a flow rate of about 5 sccm for nitrogen and about 144 sccm for argon, and about 9.
A chamber pressure of 1 mTorr was obtained. The gas was introduced for about 10 seconds before generating a plasma. Aluminum was sputtered from an aluminum target in a nitrogen and argon plasma. Sputtering of the target occurred at a power of about 4 kW for about 695 seconds. The substrate was taken out and tested for stress, layer thickness uniformity, and crystal orientation. The results are shown in Table 1 below.

Comparative Example of Single- Step Deposition An aluminum nitride film was deposited at a low chamber pressure under conditions reflecting the first aluminum nitride deposition step described above. Another aluminum nitride film was deposited under the high chamber pressure conditions of the second deposition step described above. The deposited aluminum nitride layer was then tested for layer thickness uniformity, film stress, film thickness uniformity, and crystal orientation of the deposited aluminum nitride.

Low pressure aluminum nitride deposition was performed by introducing a first substrate into the PVD chamber. Once the substrate is placed in the chamber, about 30 sc
Nitrogen gas at a flow rate of cm and argon gas at a flow rate of about 9 sccm were introduced into the chamber for about 60 seconds, bringing the chamber pressure to about 2.0 mTorr before generating a plasma. Aluminum was sputtered from an aluminum target in a nitrogen plasma and an aluminum nitride layer was deposited at a power of about 4 kW for about 710 seconds.

A high pressure aluminum nitride deposition was performed by introducing a second substrate into the PVD chamber. Once the substrate is introduced into the chamber, nitrogen and argon are supplied at a flow rate of 56 sccm and 144 sccm, respectively, to about 60 sccm.
The chamber pressure is reduced to about 9.1 seconds before generating plasma.
Introduced until millitorr. Once the plasma is generated, the aluminum target is sputtered in a nitrogen plasma and a layer of aluminum nitride is deposited at about 4 kW.
For about 710 seconds.

Table 1 below shows the two-stage deposition system and
Summarize the information of different types of one-stage deposition systems. Table 1.2 Step Aluminum Nitride Deposition and Comparative Example

Table 1 shows some important aspects of the two-step deposition of the present invention compared to the low-pressure one-step deposition process and the high-pressure one-step deposition process. The X-ray diffraction (XRD) count of the (0002) peak determines the amount of crystals formed in the (0002) orientation, where the more peak counts, the greater the amount of crystals formed in the (0002) orientation. As shown in Table 1, the large XRD count of the (0002) peak indicates that the amount of crystals formed in the (0002) orientation in the two-step deposition process is greater than in either low-pressure or high-pressure deposition. . This indicates that the first aluminum nitride step can provide an ordered crystal structure in which a large amount of aluminum nitride film to be subsequently deposited is obtained in the second aluminum nitride deposition step of the two-step deposition process. .

The rocking curve data indicates the relative amount of a crystal structure having a (0002) orientation compared to a crystal structure having another crystal orientation. In particular, the smaller or narrower the full width at half maximum (FHWM) of the rocking curve, the greater the preferred (0002) orientation of the film. In particular, the two-step deposition process of the present invention is larger (0
002) It has a degree of crystal orientation. This indicates that the film deposited by the two-step deposition process is a highly oriented (0002) crystalline film.
The preferred crystal orientation of the aluminum nitride film is SA
As can be seen from Table 1, XRs are essential to provide good electromechanical properties in W and BAW devices.
The high D count and narrow rocking curve data indicate that the deposition process according to the present invention provides high quality crystalline films.

Table 1 further shows one-stage low-pressure or one-stage of the present invention.
This shows an advantage over a high pressure deposition process. I mentioned earlier
Providing excellent quality film at the same time as two steps
The deposition process can also be performed at a practically satisfactory deposition rate (eg,> 10
00 angstroms / min). Two-stage deposition process
Processing rate is comparable to high pressure aluminum nitride method
You. In addition, the (0002) oriented filter produced according to the present invention.
Lum's total stress is a one-step low-pressure aluminum nitride deposition process
Greater than (0002) oriented film deposited at
Small. Thus, the present invention also provides low film stress (eg,
For example, about 8 × 10 ⁹High quality (0 dynes / cm)
002) Produces a film, so the layer failure during deposition
Is reduced. Finally, the present invention provides a layer compared to one-step deposition.
Thickness uniformity has also been improved. Improved layer thickness uniformity
And good electromechanical properties can be obtained
The system has uniform characteristics. According to a preferred embodiment of the present invention,
Described above, but other further embodiments of the present invention.
But without departing from the basic scope of the invention.
The scope of which is defined by the claims.
Is done.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a PVD chamber suitable for performing the PVD process of the present invention.

FIG. 2 is a simplified block diagram showing a hierarchical control structure of a computer program suitable for controlling the processing method of the present invention.

[Explanation of symbols]

 36 PVD chamber 102 Chamber surrounding 104 Target 106 Substrate support 108 Gas inlet 110 Gas outlet 116 Substrate 118 Substrate support lift assembly 124 Sputtering material 130 Magnet assembly 146 Processing cavity 152 Power supply 156 Exhaust valve 158 Exhaust pump

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Rochelle King, United States of America 94065 Redwood City, Buri Car Lane 10 (72) Inventor Hoa Kieu, United States of America 94086 Sunnyvale Belmont Terras 984-3

Claims (18)

[Claims] 1. A method for forming an aluminum nitride layer on a substrate in a processing chamber, comprising: a. Depositing a first aluminum nitride layer at a first chamber pressure; b. Depositing a second aluminum nitride layer at a second chamber pressure higher than the first chamber pressure. 2. The method of claim 1, wherein said first aluminum nitride layer is deposited at a first chamber pressure between about 1.5 mTorr and about 3 mTorr. 3. The method of claim 2, wherein the second aluminum nitride layer has a thickness of about 5
The method of claim 1, wherein the deposition is at a second chamber pressure between mTorr and about 10 mTorr. 4. The method of claim 1, wherein said first and second aluminum nitride layers are sequentially deposited in a same processing chamber. 5. The method of claim 1, wherein said first aluminum nitride layer is deposited by sputtering an aluminum target in a plasma comprising nitrogen and an inert gas. 6. The method of claim 1, wherein said second aluminum nitride layer is deposited by sputtering an aluminum target in a plasma containing nitrogen and an inert gas. 7. A method of processing a substrate in a processing chamber, comprising: a. Introducing a first nitriding process gas into the process chamber at a first chamber pressure; b. Sputtering aluminum target to first
Depositing an aluminum nitride layer of c. Introducing a second nitriding gas into the processing chamber at a second chamber pressure higher than the first chamber pressure; d. Sputtering aluminum target for second
Depositing an aluminum nitride layer of the above. 8. The method of claim 7, wherein said first chamber pressure is between about 1.5 mTorr and about 3 mTorr. 9. The method according to claim 7, wherein said first nitriding gas comprises nitrogen. 10. The method of claim 7, wherein said second chamber pressure is between about 5 mTorr and about 10 mTorr. 11. The method according to claim 7, wherein said second nitriding gas comprises nitrogen and an inert gas. 12. The method according to claim 11, wherein the first and second nitriding gases are about 4
The method of claim 7, wherein the sputtering is performed in a plasma generated at a power between kW and about 7 kW. 13. The method of claim 11, wherein said inert gas is argon. 14. The method of claim 7, wherein said substrate is maintained at a temperature between about 125 ° C. and about 500 ° C. 15. A method of forming an aluminum nitride layer on a substrate in a processing chamber, comprising: a. Aluminum target with chamber pressure about 1.5
Depositing a first aluminum nitride layer by sputtering in a nitrogen plasma between mTorr and about 3 mTorr; b. Depositing a second aluminum nitride layer by sputtering an aluminum target in a plasma of nitrogen and an inert gas at a chamber pressure between about 5 mTorr and about 10 mTorr. . 16. The method of claim 15, wherein said first aluminum nitride layer is a nucleus for said deposition of said second aluminum nitride layer. 17. The method of claim 15, wherein said inert gas is argon. 18. The method of claim 15, wherein said substrate is maintained at a temperature between about 125 ° C. and about 500 ° C.